BROWNCOATS · 2018. 12. 16. · BROWNCOATS Team 7842 Engineering Notebook - Rover Ruckus WHAT WE...

BROWNCOATSTeam 7842 Engineering Notebook - Rover Ruckus

WHAT WE DID OVER THE SUMMEROff Season

Reflections

After our 2017-2018 season ended, the team decided to set goals for the upcoming 2018-2019season. Our goal was to have a fully driveable and competitive robot within six weeks ofkickoff which would put it around October 27th. We also set scoring milestones for theupcoming season. The first milestone was being able to score one point by October 1st, thesecond was to score 100 points 3 weeks after that, and the final was to score 370 points by theWorld Championship in Houston. To achieve these goals, Ian decided to spend the summerresearching various drive trains so that when we learned the challenge at kickoff, we wouldhave a drive train mostly ready to go.

In addition to all of the Outreach that we do over the summer (which is fully described underthe Team section in this engineering notebook), we decided to hold a series of small classesand presentations to help our new team members (two of them have never done roboticsbefore) feel more comfortable on the team.

This approach of setting goals and having summer classes seems to have worked very well forus, so we plan on continuing doing these classes next summer.

! Research/Proof of Principle! Fundraiser: Building a Swing Set! Programming class led by Ian! Lessons Learned discussion! Engineering Process presentation from Jeff Stewart, Coach! Toastmaster’s presentation from Mr. Mike Baran! Helpful Building Tips from John Bateman, Student Mentor! Soldering class led by Monte Bateman, Mentor! Engineering Notebook and Photography guidelines from Cindy Stewart,

Mentor

What We Did Over the Summer - Off Season Engineering - 1 Reviewed:


Tasks Reflections

Research/Proof ofPrinciple

6-wheel shiftingdrive train

At the end of our Relic Recovery season, we decided that we wanted todesign one or more drive trains for Rover Ruckus during the off-season, so that we could immediately jump into designing for thegame, rather than focusing all of our time on the drive train.

The original concept for the first drive train was a 6 wheel drive – 4 ofwhich were omni-wheels. They were located on the corners to reduceturning scrub. This meant that the center wheel did not have to bedropped. Additionally, we wanted the drive train to shift between twodifferent ratios, as well as use bare Neverest motors (without a pre-fabricated gearbox.) with our own custom gearboxes, to increase theefficiency of the system by use of bearings. After some basic modelingof gearbox concepts, we decided to place the gearbox in between thetwo drive train plates that provide structure to each drive train side.These custom gearboxes would be made by using VEXPro 32DP and20DP gears to reduce the ~6600RPM bare NR to a useable speed. We wanted a fairly fast ratio for quick distance traveling, and a fairlyslow but strong ratio for defense or pushing matches. The two conceptratios were ~16:1 for the speed ratio, which would equate to roughly4.5ft/sec before efficiency losses, and ~35:1 for the pushing ratio,which would equate to roughly 2.5ft/sec, with far more pushing power.

We planned on using ball shifters for the shifting, with servos on camsto actuate the shifter plunger. This concept graduated to a completeCAD model before the team decided that the shifting idea wasimpractical for FTC. Shifters are heavy, and require far more complexgearboxes to utilize, which in turn requires a taller drive train side.Additionally, this adds a very large single point failure into the system,being the shifting servo.



6-wheels shifting drive train without wheels

6-wheel shifting drive train with wheels



Tasks Reflections


one speed 6-wheeldrive train

With all of these drawbacks in mind, we decided to move away fromthe shifting drive train concept, and instead create a new 6 wheel drivetrain. This one would also use bare Neverest motors, and customgearboxes, but the removal of a shifter would drastically reduce thecomplexity of the system. We would still use 4 omni-wheels in thecorners.

This idea also progressed to a full CAD model. The removal of shiftersdid indeed reduce the size and estimated weight of the drive train by asignificant amount. However, this design also had some problems.First, the drive train was very tall in the back (over 7”), which wouldmake subsystem integration very difficult. Furthermore, the belt path topower the wheels was extremely long, and very complex. Each side had4 tensioners (each of which utilizes 2 VEXPro ½” ThunderHexbearings, which allows the belt to run smoothly over the tensionerwithout much efficiency loss.). This, coupled with the complexity ofthe gearboxes made the drive train concept very expensive to produce.Finally, we later realized that the drive belt pulley didn’t have enoughbelt wrap (180 degrees of wrap on a high-load pulley is ideal to reduceskipping, we had just over 100 degrees) to consistently transfer powerto the wheels. We learned this from our recently built Relic Recoverydemo robot, which had belt skipping problems, due to the amount ofwrap on the drive pulleys.

Yet again, we decided to shelve this concept until a later date (this wasin late May). Our next project was a custom gearbox mecanum drivetrain. (early June)



Full 6-wheel drive render

Side-view One-speed 6WD full belt path



Side-view One-speed 6WD without wheels

Side-view One-speed 6WD



Tasks Reflections


Mecanum drivetrain

For this drive train, we wanted our motors to be in line with themecanum wheels, similar to our Relic Recovery swerve drive. Thiswould completely remove them from space in between the drive trainsides, allowing us a fully uninterrupted area to integrate subsystems. Toaccomplish this, the design has two horizontal plates, with 15mm REVextrusion sandwiched between them. The lower plate is where themotors mount, and the upper plate is to support bearings. The motorsface up, with 12 tooth 32DP gears pushed onto the bare motor shafts.These interface with individual (one gearbox per wheel) 80 tooth 32DPVEXPro gears, giving us a roughly 6.67:1 reduction in the first stage.After this, the vertical shaft connected to the 80t gear also has a 15tVEXPro bevel gear on it. This interfaces with another 15t VEXProbevel gear (For a 1:1 ratio). This bevel gear is on the same shaft as a 20tooth HTD 5mm belt pulley. We then have an 80t belt go from the 20tpulley to a 48t pulley, which is mounted onto the mecanum wheel. Thisresults in an overall reduction of 16:1. If we decided this is tooaggressive of a reduction for the challenge, we can replace the 20tpulley with an 18t pulley for a roughly 18:1 reduction. Each 80t belthas a tensioner, which rests in a 40mm long slot to adjust the tensioner.The tensioners use 1.125” OD bearings running on ½” hex shaft,allowing the tensioners to double as structural standoffs. This allows usto combat belt stretching or tolerance issues.

We are currently in the process of manufacturing this drive train. Itshould be at a testable stage by the end of week 1 of the Rover Ruckusseason. We’re starting with 3/16” thick polycarbonate plates to testwith. Our previous experiences with polycarbonate have been mixed.We found it to be far too flexible to handle much load. However, thethickness of that polycarbonate was 3/32”. 3/16 As such, we’re hopingthat bending won’t be an issue. If it isn’t, we will manufacture the otherside of the drive train out of polycarbonate. ” is double that. If it is anissue, we have two options. Our first option (and ideal scenario), is thatwe can laser cut 3/16” G10 fiberglass for our drive train, as it’s asstrong as aluminum and far lighter, and the same cost. If we cannotlaser cut them, we’ll manufacture the plates out of 3/16” thick 6061-T6aluminum at Calhoun’s Aerospace Training Center.



Early Mecanum Side View


Mecanum drivetrain(continued)

With the mecanum drive train design done, we started to revisit theidea of a 6 wheel drive train. This time, we decided that omni-wheelswere too thick to use effectively, and opted to return to the classiccenter wheel dropped method. In all of the following designs and ideas,the center wheel was dropped by 1/8”. This is a very common andproven drop distance for FRC and FTC teams. For the first two designconcepts, we still wanted to pursue the idea of a custom gearbox, withtwo motor inputs per side. Unfortunately, there’s far less space to workin with a 6 wheel drive train, which makes it extremely difficult tomake a custom gearbox within that space. On the third design concept,we decided to instead try Orbital 20 gearboxes, due to their exceptionalefficiency, relative to the other Neverest gearboxes. Additionally, wetried 3” wheels instead of 4” wheels, and lowered the overall drivetrain ratio accordingly to account for this. (14:1 for 3” wheels, downfrom the 16:1 previously).

This idea was moderately successful, but unfortunately had to bedelayed for the time being, as kickoff was rapidly approaching and weneeded to shift gears to get at least one drive train manufactured beforeor shortly after kickoff. However, this concept seems sound, and maypossibly be revisited for this competition or future ones, depending onthe needs of the game.



Full Mecanum DT

Mecanum Bottom View One Side



Mecanum Bottom View

Mecanum Front View



Mecanum Render

Mecanum side view



Mecanum Top View



Tasks Reflections

Fundraiser: Building aSwing Set

On May 26th, the team assembled a wooden swing set for thegranddaughter of Ms. Sheila from Lionheart Christian Academy.



Tasks Reflections

Programming Class On Friday, June 22nd, the Browncoats and FTC team 13808Time Traveler’s gathered together to listen to a presentation onbasic programming from one of our team members, Ian. We setup a projector and using sample codes and PowerPoint slides,Ian discussed everything one needed to know about gettingstarted when it comes to programming.

First, he went through how to connect the phones to the robot,and how to connect the REV Hub module. He then talked aboutuploading your programming to the phones and how OP modeswork and how to set them up.

After all of that, he walked us through how to program a robot tomove. Using the projector, he gave us example lines of codesand then demonstrated how it worked once he uploaded it to thephones.

This was a great learning experience for both teams’ rookies andthose who didn’t know much about programming!



Tasks Reflections

Lessons Learned On Friday June 29th during our regular meeting time, the team sat downto discuss our previous season and some of the things that we thoughtwe did right, lessons we learned, and things we should never do again.

Not only was this a good way to teach some of what goes into a seasonto new team members, but it was also a great way for the veteran teammembers to look back at all we accomplished and try to figure outthings we could have done differently to make the season moreefficient, but also good things we accomplished that we might want totry again in our upcoming season.

THINGS WE DID RIGHT:1. The amount and quality of outreach that the team did throughout theseason.2. A positive balance was maintained in the team bank accountthroughout the year.3. The team's very positive social media presence.4. How the Engineering Notebook came together (both in format andcontent), especially the outreach pages.5. Letting younger kids drive robots during outreach events--thisengaged many future generations of robot builders and was somethingthat no other local team did.6. The Rocket City FTC Invitational - was a fun get-together with otherteams that generated tons of goodwill. This needs to become an annualevent.

THINGS THAT WENT WRONG:1. The robot was completed much too late in the season. There was notime to practice, prepare for judging, etc.2. Too much time was spent early in the season discussing what toprototype.3. Waited way too long to commit to ideas to build.4. Committed to some ideas too much -- waited too long to abandonthem and move on to other workable solutions.5. Not enough preliminary proof of principle prototyping was done andnot enough alternative avenues were explored.



Lessons Learned (continued)

THINGS THAT WENT WRONG (continued):6. More team members needed to work on the robot.7. Waiting until the last minute to: - Write and submit engineering notebook entries. - Begin practicing for the judging presentation. - Begin working on the picture boards.

THINGS WE SHOULD NEVER DO AGAIN:1. Delay our daily engineering notebook inputs. Too much wasforgotten with the passing of time.2. Design completely in CAD and expect it to work immediately.3. Leave the judging presentation to the last minute.4. Never leave someone in the pit who is not prepared to speak to theroaming judges--Never tell the judges that they don't know anything andthat the judges should come back later. (In years past, judges sought usout and spoke to the team while in queuing--we should never expectthat to happen, especially at the higher levels of competition).5. Recruit a new team member with the implication of being tied to adonation.



Tasks Reflections

Engineering Process During our June 29th, meeting, Mr. Jeff did a presentation on theEngineering Process.

We talked about the building process we will be using for theupcoming season. Hopefully, the process will help us build ourrobot quickly and cleanly before competition. We also talkedabout the difference between prototypes and proofs of principle(POPs). Prototypes are expected to go on the robots and POPsare prototypes that show how this idea could work and why,using everyday things. The team definitely benefitted from Mr.Jeff’s presentation, and we hope to apply what we learned to thisseason.



Tasks Reflections

Toastmaster’spresentation

On July 13th, Mr. Mike Baran, a member of the local Toastmaster’s club,came to speak to us about public speaking. We started with an introductionand Mr. Mike gave some background on himself. He then handed out chartsand began instructing us. He told us how to present information and whatinformation should be shared. Mr. Mike also said that it was important tonot be judgmental when someone is speaking and to personalize yourdiscussion such as using the robot’s name or turning to a teammate whoknows more abut a certain subject. Displaying our team unity andknowledge about each individual’s skills will impress the judges, he said. After the class was over, he asked who is uncomfortable with publicspeaking; everyone but Megan raised their hands. He asked her why she iscomfortable speaking in public. She told him how her background was intheater and that she has been the only one to speak to people during outreachevents. He thought she would be the best fit to be our public speaking coach.Mr. Mike decided he wanted each of us to give a presentation about our roleon the team and assigned Megan to coach us through our presentations. Healso told us about a fund-raising opportunity, and he agreed to continue tocoach us with our public speaking.



Tasks Reflections

Helpful Building Tipsfrom John Bateman

On Friday, August 17th, John gave a brief demonstrationshowing why structures that incorporate triangles are muchstronger than structures built entirely with squares (squares canrack!). In short, use lots of cross-bracing when buildingthe internal structure of a robot. The result will be far more rigidand will last much longer.



Tasks Reflections

Soldering class Mr. Monte hosted a soldering class for the Browncoats duringthe August 24th meeting.

None of the Browncoats had ever soldered or built an electroniccircuit before, so Mr Monte first explained the basics ofsoldering and a few simple safety rules. He then gave everybodya simple LED blinker kit to build, sat everyone down at a bunchof soldering stations, and led everyone through building the kit,step-by-step.

It took almost an hour, but in the end, everyone had a workingblinker. We all gained an appreciation of how soldering is doneand felt confident enough to do it again if the need arose.



Tasks Reflections

Engineering Notebookand Photographyguidelines

At our September 14th meeting, Ms. Cindy gave us a handoutwith guidelines for how to write our Engineering Notebookentries as well as a general guideline for taking and uploadingphotographs.

Engineer Notebook Write-Ups

1. Make sure each entry has the date of the meeting or outreach event

2. Make sure each entry has your name on it! Otherwise, you get put on my nag list. Emailto me or upload to Dropbox under Documents/Engineering Notebook/Team Entries/YourName.

3. It's not just about going into detail about what's on the robot, but how you arrived at thissolution.

4. For the hardware, show how the robot has changed throughout the season, the prototypesthat you went through, and why the current design on your robot is the best. RememberWhat (what was my goal that day), Why (why did I do that) and How (how did Iaccomplish my goal).

5. For software, evolution applies as well. Show the different algorithms you went through,strategic decisions for autonomous, and why the current software on your robot is thebest. Remember: write what you did, why you did that, and how you did that.

6. For the outreach section of the engineering notebook, it's important to emphasize theimpact of the events. In this section, pictures are quite important. Try to select ones thatshow interaction, the depth of the outreach, and how many people it impacted.

7. In general, try to implement many visuals. Pictures, flowcharts, and graphics help drawattention to the points that you're emphasizing.

8. While it has a “journal” type structure to it, this is not a diary. A list of people inattendance and then a one-liner about “we worked on the robot” is not sufficient. Hereare the guidelines from the manual.



This journey goes beyond recording the day to day “here’s what we did” or just listing“we met today”. It explores questions like:• What is the agenda for today?• Why are you meeting?• What are the goals for today?• What decisions did your Team make in forming the Team, creating the robot,

writing the program, the outreach projects, etc.?• Why did you make that choice when building your robot, coded the software that

way, chose that group of individuals to outreach to, etc.?• What was the impact on your Team, robot, or community when you made that

decision?• What is the next step?

Photographs(before uploading to Dropbox)


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